alpha-pyrone and method of preparing it



Patented Nov. 16, 1943 winner Indiana No Drawing@ .imn'mitiox-aMamaai, 1941 w lseicarito..sfiamigAi c Tliecompositions of thisl invention; 'v'vl."1en-"adLr ministerewto ether-ized' cats; lowrthei-bilood prese;

sureofthesejanimals; and these compositions' are therefoi'es iislefuiy asfdepre'ssoiniagteri'als;4 "f

The compositions of thisinventiom'are' representedby-theformulas?" /og 'f (1) iv- \oH l R-t I v'cfg 1=oYV Hooo-o.\ f/ o =o O/ 0. in which R isanaliphaticgroupl such as a straight chain aliphatic group.

The compositions of this invention are prepared by reacting a compound represented by the formula: y

in: whichY Ribas-the samer-meaningl asf beforez with malonic'acid in. the presence-pfff pyridine?y actionA mayfbcrepresentedibytlie following'eqna Tha ifnfa-butene-'lfoic acm formed iarred, frein. rsyridine and subjected; #Q the ammorba;

primacy alcohol, (RioHginwnicn ai i's `anfaiky1y radical). in'the. presence o ia mneralgacfdl. 4Such Y as sulfuric. oi; hydrochloric. aci'dto yield an1estc 1" of the Lancaume-190m acid; Desirabliajjthealcohol' naam# gr,'eater trailmeenten amms subjectedtoathe;action.I ofzans esten' ofV -oxaIicf acid'.

[(COORalain-iwhioh Rzzs San; alkyli radicalgflpreff-. erably the methyl-.or ethyl radical] ine-the presience of potassium ion togyield thepotassiunisalt Y of Rir-RL--carhalkoxyfSrhydroxy-Zepentadiene-l-oate; Preferably the reaction is]carriecliV1 out in an inert solvent, such as ether, and in the presence of a lower alkyl alcohol, such'as methyl e-GH- CH @Harlow-aimer or ethyl alcohol. The `action whichitalie'sigilace` may be represented by the following equation:

(5i R- oHl-`oH=oH-CoojRH-(oo'oiwl R*o-on=ouroooai-l-R-2oiig 1 o- 0K -i-H The "resultingA potassium` saltV is treatedwitli" a' Y? dilute acid, such as hydrochloricacid or acetic acid; `tosiilostitutea hydrogenlion. for the potasf siuml. ion in thatpotassiimt salt, The. action which' takesplace InayfY berepresented-by theQfolg aqueous solution of a mineralifacidf'such? as-hy drochloriqaciito yield a -R-S-carboxy--hy- 'l which takesplacemayfberepiresented by the iol-1 1 1 P reiabli the {f cactibriiscarried hat at' tmi iiacd iis Separated'ad then Subjcted to the action l`o`f` a solution of hydrogen bromide in alower aliphatic acid such as acetic acid toyi'eld a 5-substitutd'-SicarboXy-a-pyrone! The action which takes place may be reprej sented by the following equation:

' Her 'n.-o CH o-on Kyu-5:hsiculomuze;@perita-4 `einen 1+ foon Y f movedzby mtration.

Y The crudo product is unstable and should io'susav Preferably the reaction is carried out in a'sealed 1 Vvessel and ata temperature of about 150 C.

`Alternately, the R1-4-Rv-5-carbalkoxy-5-hydroxy-2,4pentadiene1oate may be subjected to the action of hydrogen bromideto yield a 5-sub-l stituted--carboxy-a-pyrone. This actionrmay be represented by the following equation: Y'

. The 5-substituted6 Y sired -substituted-a-pyrone.

takes place may be Typical examples of the compositions of this invention and ofmethods `ofpreparing them are` as follows :j .l

' 7.8 g. of potassium and '34 acc. of absolute, ethyl alcohol in 50 cc. of anhydrous etherga mixture .of 29.2 g. of diethyl oxalate and cc. of anhy- `drous.` ether isv added dropwise with'c'areful ex' clusion of Mmoisture. VPreferably the reaction mixture is kept at about 0 C. After 15 minutes a' solution -of 25.6 g, of ethyl 2-pentane-1-oate in YV20 cc. of vdry ether is added with shaking. The res -carboXy-u-pyrone is then Y subjected to the action of copper to yield the def f f The action which represented b y the following trated hydrochloric-acid or fromalmixture pofl actionmixtureis then allowed to stand at 0 C. for

l15 hours. During-.this time the desired potassium n salt of ,ethyl-4fmethyl-Tcarbethoxyf-E-hydroxy2,f1pentadiene-lfoate isformed.;v The 'ree action=which takes place may bey represented'by thefollowing equationL 1 zg Vou'sciwcn'-ou=o o ooms? (cecchini -V--OK :13: Gzl'aH". I oochH't` 'A 1 The thick yellow 'mass of crystals ofpotassium salt is stirred with an equal" volume ofpetroleum ether andthe crystalline,potassiumY salt is separated by filtration. The potassium salt is dissolved in about 750.cc. of icje'water 'and icecold dilute acetic acid Ais slowlyfadded until no further precipitate is formed. After maintaining thereactionmixture at 0 C.'forseve'raLl'iurs,v

" the; vdesired .orystautue Y,othyi-ziemsthyirsosrb-' ethoxy95-hydroxyzAepentadiene '1T-cate 'L is` re- A The vactionihi'clrtakes place may be representedby the following' edua-r tion: 'Y Y (i2) :ons-o-ourcnl-oooosn. f.. v

C. andthe mixture is shaken until completely Y ldissolvedffhey solution is then reiluxed for .about 1hour andthen treated with decolorizing carbon. After removal of the solvent, the desired 4-methyl--carboxy-5hydroxy2,4 pentadienev-l-oicacid remains as a crystallinesolid. It may be recrystallized preferablyfrorn-concenf acetone andv petroleum ether and ,meltsV at.'A about 161-162F C., lcorrected. An kanalysis reveals 49.2 vpercent Vcarbon and 4 .8 'percent.hydrogen whichIl compares with theoretical -values-.of`f18-9percent carbon and 4.7 percent hydrogen.. TheA action which takes placel may be'represented bythe foly lowing equation: V(is) oHo'-oH=oH-c o o CHs Nine grams of 4-methyl-5-carboxy-5-hydroxyf= 2,4-pentadiene-l-oicv acid are heated at 150 C. for 2 hours in a sealed tube with 30 oc. of glacial acetic acid, which.l has been previouslyfsaturated' with hydrogen, bromide Yat. 0 .'C`. Duringthis time the .desired v5fmethyl-S-carboxy-u-pyioneis formed.` The action which takesY place mayxlbe. represented by the Vfollowing equation:

- The solvent isremoved from 'the reaction, mixgv tur'efand the crystallineresidue offf-methyl' A ca rboxyj-a-pyrone may be'jrecrystallized prefe'rfL ablyffromzwa'ter with decolorizing carbonv or from* acticfacid or from acetone.V yIt melts at about 2099-211" 0., corrected.: yAn'analysis reveals 551,9' Y A percentgcarbon and 4.1 percent.' hydrogen Yyvhiclrf compares with theoretical values" of 54,5p'ercent' carbon .and`r3.`9) percent hydrogen-- k An intimatemixture of 250 mg; of 5`methyl-sli"`4 carboxy-a-pyrone and 2.5 g.v of freshly reduced copper powder is yplaeed'ina-bent glass tube and covered witha layerpfpure cgpper'powder. The i mixture is then heated vgently with a free llame and the desired -methyl-fpyrone distills fromv the mixtures. The action which takospmoumayf be represented by the .v following equation'z..y

i ammw comme'. maybe; puvmeafm emulation and melts at about 17-19 CLJ- methyl-a-pyrone dissolyes in an alkaline solution with a yellow color,.deposits silver from an ammoniacal silver solutibn and has a characteristic l odor of fresh hay: An ana/lysis reveals 65.0 percent carbon and 5.6 percent hydrogen whichcomcarbo@ and" 5.5;l pement. 1rimasegjm..

pares with. theroeticalFV values of. .65aA percent.

Exam m-Prepamtiom o# v-5:'-armztfltylll 'heat'edfor threehnursari miic. with 35 cc. of

glacial acetic acidi, which" been previously saturated with hydrogen bromide at C. During this time, the -methyl-G-carboxy-a-pyrone is formed. The desired y5-methyl-6carboxy-ugpyrone is isolated exactly as` described in Exam# ple 1. l

EXAMPLE 3.-Preparaticm of Sfethyl-a-pyrone The ethyl 4 ethyl-5-carbethoxy-5-hydroxy- 2,4-pentadiene-1-oate is produced from ethyl-2.

l theoretical values of 572 percent carbon and 4,8

percent hydrogen. The 5ethyl--.carboxy-aa-f` am' which; ist repneserltedirby* the formula: 1 y. .i

vin which R is an aliphatic hydrocarbon group selected from the class consisting of the methyl group and its homologues. 5. 5-ethyl-V6-carboxy-a-pyrone which is represented by the formula:

pyrone is heated with copper exactly as described for the analogous compound in Example 1 to yield -ethyl-a-pyrone which may be purified by distillation. It shows a refractive index value of mp2s 1.5118. Analysis reveals 67.5 percent carbony and 6.7 percent hydrogen which compares with theoretical values of 67.7 percent carbon and 6.5

percent hydrogen. The S-ethyl--pyrone haslthe While preferred embodiments of this invention have been described, various modifications may be made therein without departing from the scope of the appended` claims.

What is claimed is:

1. A -substituteda-pyrone which is repre@ f sented bythe formula:

cH R-c/ \cH ll Y on =o \O in which R is analiphaticV hydrocarbong'roup selected from the class consisting of the methyl Y group and its homologues.

2. -methyl-.a-pyrone which is represented by the formula: l Y

CHr-C Y.

c I c c 6. The process of'preparing a 5-substitutediz-pyrone which comprises subjecting 4-R-,5-carboxyl-5-hydroxy2,4pentadienel-oic acid, iny which R is an aliphatic hydrocarbon group selected from the class consisting of the methyl group and its` homologues, toV the action of hydrogen bromide to form 5-R-6-carboxy-a-p.

pyrone and subjecting the said 5-R-6-carboxy-upyrone to the action of copper to form 5-R-- pyrone.

7. The process of preparing av5substituted v a-,Dyrone which comprises subjecting 5R6car boxy-cpyrone, in WhichR is an aliphatic hydrocarbon group selected from the class consisting of the methyl 'group and its homologues, to the action ofv copper to form -R-a-pyrone.

' 8. 'I'he processof preparing a 5-substituted-6- carboxy-a-pyrone which comprises subjecting 4- R 5 carboxy 5-11ydroxy-2,4pentadiene1oic acld,. in which R is an aliphatic hydrocarbon group selected from the class consisting of the vmethyl group and its homologues, to the action of hydrogen: bromide to form -R--carboxy-apyrone. v

9. The process of preparing a -substituted-- pyrone which comprises subjecting a compound -having the formula:

na-cHz-CH in which R is-an anphaticfhydrocarbon group selected vfrom the class consisting of the methyl group and its homologues, to the action Y of malonic acid in the presence of pyridine tc produce 4Rbutene`2oic acid, reacting the said 4- R-butene-Z-oic' acid with a primary alcohol having the formula:

in which R1 is an alkyl group, to form R1-4-R-2- butenefK-oatev with4 an ester of xoxaglio-a-dghaving the formula: i.

with Yan aqueousacd solution, treating.the resulting product with-alstrongwmineralacid toA diene-l-oate, treating the said potassium salt 1-oio acid, subjecting the resulting product to the action of hydrogen bromide Vto Vform 5R6 carboxy-a-py'rone and subjecting the said5-R-6- forni 5-R-a-pyrone.

- carboxy-oi-pyrone. toV theaction of copper to "l 1';10.;, AnLa-pyrone whiohiis -represent-,eed .by the@ l following for-mula:

in vhich Rt'is 'an alil-Iniiat'io jhydrotaronu" grotto selected from the -classeonsistig of themeth'yi group andv its homologues and-'Bris Ya member selected, from .the classi Y consisting f of hydrogen andthe carboxylic; group y. A

fl i "JosEFj CERTIFICATE oF CORRECTION. Patent No. 2, 551;,180.

, November 16, 19li5. vROBERT C. ELDERFIELD, 'ET-AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 2, first column, line 14.9, for that portion of the formula reading and that the said Letters Patent should be read with this correction therein that the same may conform to the record ofthe case inthe Patent Office.

Signed and sealed this lst day of February, A. D. 19ML.

Henry Van Arsdale (Seal) vActing Commissioner of Patents. 

